LTC4097 查看數據表（PDF） - Linear Technology

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LTC4097

USB/Wall Adapter Standalone Li-Ion/Polymer Battery Charger

Linear Technology 

LTC4097

OPERATION

The LTC4097 is designed to efficiently manage charging

a single-cell lithium-ion battery from two separate power

sources: a wall adapter and USB power bus. Using the

constant-current/constant-voltage algorithm, the charger

can deliver up to 1.2A of charge current from the wall

adapter supply or up to 1A of charge current from the

USB supply with a final float voltage accuracy of ±0.6%.

The LTC4097 has two internal P-channel power MOSFETs,

thermal regulation and shut down circuitry. No blocking

diodes or external sense resistors are required.

Power Source Selection

The LTC4097 can charge a battery from either the wall

adapter input or the USB port input. The LTC4097 automati-

cally senses the presence of voltage at each input. If both

power sources are present, the LTC4097 defaults to the

wall adapter source provided sufficient power is present

at the DCIN input. “Sufficient power” is defined as:

• Supply voltage is greater than the UVLO threshold.

• Supply voltage is greater than the battery voltage by

30mV (100mV or 150mV rising, 30mV falling).

The VNTC output pin indicates that sufficient input voltage

is available. Table 1 describes the behavior of the power

source selection.

Table 1. Power Source Selection

VDCIN > 4.2V and

VDCIN > BAT + 30mV

VUSBIN > 4V and

VUSBIN > BAT + 30mV

Charger powered from

wall adapter source;

USBIN current < 25µA

VUSBIN < 4V or

VUSBIN < BAT + 30mV

Charger powered from

wall adapter source

VDCIN < 4.2V or

VDCIN < BAT + 30mV

Charger powered from No charging

USB source

Programming and Monitoring Charge Current

The charge current delivered to the battery from the wall

adapter supply is programmed using a single resistor from

the IDC pin to ground.

RIDC

=

1000V

ICHRG(DC)

,

ICHRG(DC)

=

1000V

RIDC

Similarly, the charge current from the USB supply is

programmed using a single resistor from the IUSB pin

to ground. Setting HPWR pin to its high state will select

100% of the programmed charge current, while setting

HPWR to its low state will select 20% of the programmed

charge current.

RIUSB

=

1000V

ICHRG(USB)

(HPWR = HIGH)

ICHRG(USB)

=

1000V

RIUSB

(HPWR

= HIGH)

200V

ICHRG(USB) = RIUSB (HPWR = LOW)

Charge current out of the BAT pin can be determined at

any time by monitoring the IDC or IUSB pin voltage and

applying the following equations:

IBAT

=

VIDC

RIDC

• 1000, (charging

from

wall

adapter)

IBAT

=

VIUSB

RIUSB

•

1000,

(charging from USBsupply, HPWR = HIGH)

IBAT

=

VIUSB

RIUSB

•

200,

(charging from USBsupply, HPWR = LOW)

4097f

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